The present invention relates to a synthetic resin composition having an excellent flame resistance, and more particularly to a flame resistant resin composition containing as a flame retarder a finely divided red phosphorus coated with a thermosetting resin.
It is known to employ halogen compounds with flame retarding assistants such as antimony trioxide to impart a flame resistance to synthetic resins. However, these known flame retarders have the disadvantages of lowering of physical property, including tensile strength, and bleeding due to bad dispersibility. It is disclosed in Japanese Unexamined Patent Publication (Tokkyo Kokai) No. 4598/1973 that a flame resistance can be imparted to polyester resins by addition of red phosphorus. However, in a combustion test of a polyester composition containing red phosporus according to UL-94 there is frequently observed the phenomenon that the burnt resin droplets cause cotton placed below to ignite, namely the so-called dripping phenomenon, and accordingly a stable, high flame resistance cannot be obtained by the use of red phosphorus. Also, since red phosphorus is subject to chemical reactions, a composition containing it has the disadvantage that the heat stability and the electric characteristics are lowered, to say nothing of difficulty in handling.